Microbiology
Zoonotic Diseases and Miscellaneous Infections
Zoonotic and public-health infections for MBBS: rabies, leptospirosis, plague, rickettsial fevers, dengue, malaria and HIV, mapped to NMC codes MI8.1 to MI8.8.
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Clinically reviewed by Dr Shameer Deen, MBBS, MS, MRCS
Zoonotic Diseases and Miscellaneous Infections
Zoonotic and public-health infections for MBBS: rabies, leptospirosis, plague, rickettsial fevers, dengue, malaria and HIV, mapped to NMC codes MI8.1 to MI8.8.
This chapter gathers the zoonotic and miscellaneous infections of public-health importance. It covers rabies, brucellosis, leptospirosis, plague, anthrax and rickettsial and arboviral fevers, along with human immunodeficiency virus, hospital-acquired infection and antimicrobial resistance, and the prevention strategies for each.
High-yield: Zoonotic Diseases and Miscellaneous Infections
- Rabies is a zoonotic viral encephalitis transmitted by dog bites and is almost always fatal once symptoms appear.
- Post-exposure prophylaxis for rabies combines thorough wound washing, rabies immunoglobulin and a vaccine course.
- Brucellosis is acquired from unpasteurised milk and animal contact and causes an undulant fever, diagnosed by serology and blood culture.
- Leptospirosis is spread through water contaminated with rodent urine and can cause Weil's disease with jaundice and renal failure.
- Plague is caused by Yersinia pestis, transmitted by the rat flea, and produces buboes in its bubonic form.
- Anthrax is caused by Bacillus anthracis and its cutaneous form shows a painless black eschar.
- Scrub typhus is caused by Orientia tsutsugamushi, transmitted by mites, and shows a characteristic eschar at the bite site.
- Rickettsial fevers are diagnosed by the Weil-Felix test and treated with doxycycline.
- Malaria is caused by Plasmodium species transmitted by the female Anopheles mosquito and diagnosed by peripheral blood smear.
- Dengue is a mosquito-borne flavivirus that can progress to dengue haemorrhagic fever and shock.
- Chikungunya, spread by Aedes mosquitoes, causes fever with severe joint pains.
- The human immunodeficiency virus targets CD4 T cells and progressively causes acquired immunodeficiency syndrome.
- Hospital-acquired infections are frequently caused by multidrug-resistant organisms such as MRSA and Pseudomonas.
- Standard precautions and hand hygiene are the foundation of hospital infection control.
- Emerging and re-emerging infections require surveillance, laboratory capacity and vaccination programmes to contain.
Zoonoses and their vectors
- Rabies: Rhabdovirus from dog bite. Fatal encephalitis, prevented by post-exposure prophylaxis.
- Leptospirosis: Leptospira from rodent-urine water. Weil's disease with jaundice and renal failure.
- Plague: Yersinia pestis via rat flea. Bubonic and pneumonic forms.
- Scrub typhus: Orientia tsutsugamushi via mites. Eschar, treated with doxycycline.
NMC competencies in this chapter
- MI8.1: Zoonotic bacterial infections: brucellosis, leptospirosis, plague and anthrax
- MI8.2: Rabies and other zoonotic viral infections
- MI8.3: Rickettsial infections and their laboratory diagnosis
- MI8.4: Arboviral and vector-borne infections including dengue and chikungunya
- MI8.5: Malaria and other parasitic zoonoses
- MI8.6: Human immunodeficiency virus and opportunistic infections
- MI8.7: Hospital-acquired infection and antimicrobial resistance
- MI8.8: Prevention, vaccination and infection control practices
Frequently Asked Questions
What is the post-exposure prophylaxis for rabies?
It combines immediate thorough washing of the wound with soap and water, infiltration of rabies immunoglobulin around the wound in category three exposures, and a full course of rabies vaccine, because established rabies is almost always fatal.
How is scrub typhus recognised and treated?
Scrub typhus presents with fever and often a black eschar at the mite bite site, is supported by the Weil-Felix test, and responds well to doxycycline, which is why early recognition matters.
How does the human immunodeficiency virus cause immunodeficiency?
It infects and progressively depletes CD4 T-helper cells, weakening cell-mediated immunity until the patient becomes vulnerable to opportunistic infections and defines acquired immunodeficiency syndrome.
Why is antimicrobial resistance a growing concern?
Multidrug-resistant hospital organisms such as MRSA and resistant Gram-negative bacilli limit treatment options, so surveillance, rational antibiotic use and infection control are central to containing them.
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